The full text of the DCO version 1.1 (the current version as of 2011) is:

Developer's Certificate of Origin 1.1
By making a contribution to this project, I certify that:
(a) The contribution was created in whole or in part by me and I
have the right to submit it under the open source license
indicated in the file; or
(b) The contribution is based upon previous work that, to the best
of my knowledge, is covered under an appropriate open source
license and I have the right under that license to submit that
work with modifications, whether created in whole or in part
by me, under the same open source license (unless I am
permitted to submit under a different license), as indicated
in the file; or
(c) The contribution was provided directly to me by some other
person who certified (a), (b) or (c) and I have not modified
it.
(d) I understand and agree that this project and the contribution
are public and that a record of the contribution (including all
personal information I submit with it, including my sign-off) is
maintained indefinitely and may be redistributed consistent with
this project or the open source license(s) involved.

Example

Here is an example Signed-off-by line, that indicates the submitter accepts the DCO:

Signed-off-by: John Doe <john.doe@hisdomain.com>

Older versions

The original DCO, version 1.0, read:

Developer's Certificate of Origin 1.0
By making a contribution to this project, I certify that:
(a) The contribution was created in whole or in part by me and I have the right
to submit it under the open source license indicated in the file; or
(b) The contribution is based upon previous work that, to the best of my knowledge,
is covered under an appropriate open source license and I have the right under that
license to submit that work with modifications, whether created in whole or in part
by me, under the same open source license (unless I am permitted to submit under a
different license), as indicated in the file; or
(c) The contribution was provided directly to me by some other person who
certified (a), (b) or (c) and I have not modified it.